I missed your age but almost everyone with any mileage on them will test positive for mono. Takes a skilled doc to tell if it is acute or not. In addition to sleep study, get your testosterone checked also. Even in your 20's and 30's.
Hate to be overly simplistic but maybe you are just tired and bored. Take a real break and do some other things and come back in a month or so. May not be an option if you are training for something. I believe ( zero proof of this mind you) we evolved around long breaks and changes in activity levels. Seasons, availability of different foods, battles, rainy seasons, etc. I believe we have to make changes or walk away from our chosen activities from time to time.